Cross-etiology comparisons provide important information that can help practitioners establish criteria for differential diagnosis and tailor interventions towards the source of children’s difficulties. This study examined the extent to which parent rating scales of socioemotional behavioral difficulties differentiate cases of attention-deficit/hyperactivity disorder (ADHD) from cases of specific language impairment (SLI), and typical development (TD). Parents of 60 children (7–8 years) completed the Child Behavior Checklist (Achenbach & Rescorla, 2001) and the Conners Parent Rating Scale-Revised (Conners, 2004). Significant differences were observed between ratings provided for the children with ADHD and the children with SLI and TD across several scales which assessed behavioral and emotional difficulties. Most of the observed differences between ratings provided for the SLI and TD groups were not significant when nonverbal IQ was treated as a covariate or when syndrome scales were adjusted for the presence of language and academic items. In contrast, these adjustments had little impact on observed differences between the children with ADHD and the other groups. These results highlight important and clinically useful differences between the scope and the scale of socioemotional behavior difficulties associated with ADHD and SLI.